QFE, QNH, Zero set at any point, as a means to eliminate mid-air's in a traffic pattern?
What about covering up the altimeter....fly what looks right....and keep your Mark I's looking outside the windows as a means to traffic avoidance.
The key is arriving at a "height" above ground....and as no one is perfect in altitude control...altimeters have errors....and setting numbers maybe as much as an hour old.....or older....just what relevance does the altimeter reading have to do with traffic avoidance anyway?
You are only guessing at your height at the best of times anyway!
I would think flying a common track over the ground that is shared by all the other traffic in "the circuit" would go much farther in preventing a collision.